87 Jimmy - Engine Mystery - PLEASE HELP !

[budadavid]

Hello All -

I have a 87 Jimmy with a new GM crate motor, RV cam, starter, alternator, battery, ignition module, ignition coil, pick up coil, computer, throttle body, oil pump, distributor, cap, plugs, wires, EGR, air flow sensor: BUT - it wont run once it gets up to temp. It will start, run great (you can even drive it for a mile or two) and then it stutters, hesitates. You can then shut it off, and turn it back on and do that again for two miles.

I have been working with my mechanic on this for month and we are out of ideas - I will try anything before I take it to the Engine Dr. down the road at $95.00 / hr.

Please advise -

 

[diesel4me]

I didn't see "fuel filter" on the list of replaced parts..or coolant temp sensor...two things I'd be suspicious of,going by your symptoms....

I've seen ECM's that work perfect when cold but crap out when hot ,and a few that wouldn't work in cold weather unless you warmed them up with a hair drier,then the truck would start right up ...it could be a wire problem,one thats coroded and builds more resistance after a few minutes with voltage going thru it...crank sensor or pick up coil maybe too??..they dont always set a code or make the check engine light come on..

 

[texas4x4rebel]

What about your o2 sensor in the exhaust sounds like maybe ones your engine warms up and the ecu goes into close loop the problem starts maybe a ecu or o2 sensor.